This invention generally relates to remote control systems and more specifically is directed to a remote control system and method therefor for controlling several operating functions in each of a plurality of controlled devices.
Wireless remote control systems have been in use for many years for remotely controlling such things as model airplanes, toy automobiles, a great variety of industrial machines, and home entertainment devices. The systems are generally implemented by means of either an ultrasonic or an optical, e.g., infrared, communication link. The transmitted signals are generated in response to user inputs provided to a matrix-type keyboard. Each key on the keyboard represents a controllable function available in the device for regulating its operation. The number of such controllable functions is generally limited by the number of keys that can be conveniently placed on the keyboard, rather than by the number of functions which can be performed by the circuitry insde the controlled device.
The tendency today is toward controlling not only more functions in the remotely operated device, but also toward controlling more than one, and in many cases a large number of remote devices. This is particularly true in the home environment where entertainment appliances are being used in increasingly larger numbers. The desirability of remotely controlling several home entertainment devices by means of a single control panel is obvious. However, the increasing number of available, controllable functions in combination with the ever increasing number of home entertainment devices has severely taxed current remote control systems. In addition, some of the techniques recently undertaken for controlling several such devices have involved such new designs and radical departures from earlier remote control systems that integration of these earlier systems with the new approaches is not technically feasible as a practical matter.
To realize these additional control and address functions without adding a corresponding number of different control frequencies or transmitted pulse codes, some of the newer systems use combinations of a basic set of control signals transmitted either in certain sequences or coincidentally. In this way, for instance, a few basic control signals may be utilized to control a larger number of different functions and devices. However, this has led to significant complexity at the receiver end of the remote control system, particularly in terms of decoding schemes, while at the same time allowing for the possibility of greater confusion of the inexperienced user and enhanced susceptibility to unwanted noise.
One approach to remotely controlling several devices by means of either an ultrasonic or infrared link is described in "A Pulse Position Modulation Transmission System For Remote Control Of A TV Set", IEEE Journal of Solid State Circuits, Vol. SC-11, No. 6, Pages 801-808, December 1976, by Casier, et al. In this article is described a pulse position modulation transmission system in which up to 32 commands can be generated by means of an 8.times.4 matrix keyboard and encoded into 5-bit pulse position modulated (PPM) words. Also disclosed is the use of a double throw switch incorporated in the keyboard to insert a different RC time constant in the transmitter circuit in providing for the generation of a second set of 32 control signals for controlling, for example, another device. Another approach is disclosed in West German Pat. No. 27 46 532 filed Oct. 17, 1977 to Kanow which contemplates the use of a remote control system for radio and television receivers utilizing separate data and address buses connected to a single chip microcomputer in the remote control receiver for processing address and function control signals.
U.S. Pat. No. 4,010,423 to Collins, et al and assigned to the assignee of the present application describes a remote control system in which the frequency of input control signals is used to selectively initiate a first mode in which two preselected frequencies control a multi-state bidirectional function (volume) and a second mode in which the same two preselected frequencies control a multi-state cyclic function (volume) and a distinct bistable function (picture control). Still another approach to expanding the capability of remote control systems is disclosed in U.S. patent application Ser. No. 57,053, filed July 12, 1979 U.S. Pat. No. 4,377,006 in the names of Collins and Hendrickson in which is disclosed a remote control system for a television receiver in which a multibit code identifying a selected function of the television receiver includes a plurality of data bits comprised of either a single pulse representing a first logic state or a grouping of at least two relatively closely spaced pulses representing a second logic state. By selectively positioning these two logic states in various combinations as the start bit, or bits, of a logic word, various functions and devices may be addressed and controlled by a single remote transmitter. Finally, U.S. Pat. No. 4,291,385 to Osborne, et al is directed to a calculator keyboard for allowing a single key to perform various functions as desired. This is accomplished by means of a prefix key which is selected prior to engagement of the desired function key.
The present invention is intended to avoid the aforementioned limitations by providing a remote control system and method therefor which permits a large number of devices each having a plurality of functions to be simultaneously controlled without the need for additional input controls or mode switches. In addition, this increased control capability is made available without the use of a microcomputer, additional data lines, or increased bit size of the control words.